1. Field of the Invention
This invention relates to casters generally and particularly to a retractable caster which may be lowered to mobilize a storage container and then retracted for stacking or immobilizing the container. Still more particularly, this invention relates to a retractable caster having its own chamber beneath the container into which the caster retracts, and which spaces apart containers for fork lift insertion.
2. Description of Related Art
Casters permanently attached to large storage containers permit easy movement of the containers across load bearing surfaces. When such containers are stacked on top of one another, however, the convenience of the caster can be a hazard unless the casters are immobilized. Likewise, it is desirable sometimes to move a container into place on a floor and then prevent it from easily being moved from the selected spot. Convenient means for preventing castered containers from rolling about uncontrolled is highly desirable.
Casters on stacked containers also can be damaged by fork lifts. Fork lift tines can be inserted between casters to lift a container, but accuracy by fork lift drivers is more ideal than reality. The forks smash into unprotected casters, damaging them and preventing them from serving their intended purpose. A need exists for means to protect casters on stacked containers from damage by fork lifts.
Various means have been developed in response to the foregoing needs. Most casters include built-in locks which frictionally hamper rotation of the caster""s axle or wheel when rolling is undesirable. Such locks may become contaminated or wear out with usage, however, and release on their own. Locks also do nothing to protect casters from fork lifts.
Known retractable caster systems allow containers to be stacked safely, but do not provide spacing between stacked containers. Such casters typically retract into a recess within the container itself, allowing the containers to be stacked one on top of another. Such arrangements consume container space, however, making the container less efficient. They also do not vertically space apart stacked containers so fork lift tines may be inserted beneath each container. If spacing is necessary, pallets or other devices must be employed to create the separation between containers. A caster retractable into an external chamber on the container bottom would permit safe fork lift insertion and prevent stacked containers from rolling about on top of each other.
Among known retractable casters systems, most require that the weight of the container be relieved while lowering or retracting the caster. This usually involves lifting the container with a fork lift or jacks while someone operates the caster mechanism. The container then may be set down onto its bottom or the caster. A retractable caster operable under load would save time and labor.
Accordingly, it is an object of this invention to provide a retractable caster which is protected from damage from fork lifts.
It is another object of this invention to provide a retractable caster with its own retraction chamber, said chamber doubling as a spacer between stacked containers.
It is another object of this invention to provide a retractable caster that does not consume container space.
It is yet another object of this invention to provide a retractable caster that eliminates the need for pallets between storage containers.
It is yet another object of this invention to provide a retractable caster system which may be operated under load.
The foregoing and other objects of this invention are achieved by providing a retractable caster system composed of a rectangular steel box defining a chamber, a plurality of which may be attached to the bottom of a storage container to elevate the container above a surface upon which it rests. Inside the chamber, a caster is mounted to a hinged plate which pivots near the bottom of one sidewall of the chamber. The plate articulates between a substantially vertical position, with the caster fully retracted into the chamber, and a horizontal position with the caster wheel protruding beneath the chamber. A coiled spring biases the plate toward a vertical position, and an automatic locking mechanism holds the caster in its extended position. The caster may be raised and lowered without separately supporting the weight of the container.